Preparation of styrene copolymers



etented Feb.

No Drawing. Appiication m S No. 81%,28tt

' nol, acetone, carbon tetrachloride, petroleum ether, ethyl acetate, etc. They are also characterized by their iriability and opaque, white appearance, in contrast to the tough, transparent,

glass-like co=polymers previously known. The

new products, however, are usually capable of being molded to form clear, transparent molded articles which are substantially insoluble and nonswelling in organic solvents and which are somewhat more resistant to distortion by heat than is molded polystyrene. These products are herein referred to as co-polymers of styrene, although, as stated in the above-mentioned application, their exact molecular structure is not definitely no According to said co-pending application, the new insoluble and non-swelling co-polymers are prepared by polymerizing at a temperature below about 110 0., a mixture of monomeric styrene and an unsaturated ester co-polymerizlng agent containing at least two groups in the molecule. Examples of such esters are diallyl maleate, allyl cinnamate, diallyl oxalate, di-(2-chloroallyl) adipate, trimethallyl phosphate, cinnamyl acrylate, 2-chloroallyl acrylate, ethylene dicinnamate, z-chloroallyl furoate, the dicinnamate of 1.4-dioxanediol-2.3, methallyl cinnamate, crotyl crotonate, allyl methacrylate, 2-chloroallyl crotonate, 2-ethylallyl 'vinylacetate, diallyl succinate, etc. The product initially obtained by operating in this manner is a mixture comprising the desired insoluble, non-swelling type of co-polymer and more or less of a tough, glass-like type of co- 1 polymer which is capable of being swelled in ben- Gerald E. Golan and Jo mob, acre to The i d, h... a coration oi ltfichiw Ghemical 6cmy 17, me,

zene and similar aromatic hydrocarbon solvents.

The proportions in which the two types of cop lymers are formed depend upon a number of factors, including the particular co-polymerizing agent employed, the conditions under which the tic-polymerization is carried out, the purity of the swelling product obtained as the sole product.

We have now found that the yield of the insoluble, non-swelling co-polymer may be considerably increased by carrying out the co-polymerization in the presence of a polymerization inhibitor for the glass-like, swelling type of co-polymer. Apparently the poor yields of the non-swelling product heretofore obtained are due to the higher rate of formation of the glass-like swelling type of product. Accordingly, by retarding or inhibiting the formation of the latter, co-polymerization to form the insoluble, non-swelling co-polymer is permitted to proceed more nearly to completion with resultant increased yield of the desired product. The inhibitors which we have found suited to this purpose are those materials which .are capable of inhibiting the polymerization of substantially pure monomeric styrene. Many such materials are known in the art, for example, phenyl-naphthylamine, diaminoazobenzene, pphenylenediamine, etc. The organic inhibitors for the polymerization of styrene appear to be best suited for use according to the invention, and a preferred group of such inhibitors includes phenyl-alphanaphthylamine, 2-(4 phenylazo phencxy) ethanol, arylazo-substituted phenols, and arylazo-substituted arylamines.

In preparing the insoluble and non-swelling type of styrene co-polymer according to the invention, a, mixture of monomeric styrene and an unsaturated ester containing at least two groups is polymerized by heating at a temperature below about 110 0., preferably at 50-85 C. in the presence of an amount of the inhibitor sufiicient to retard substantially the formation of the glass-like swelling type of co-polymer but insufiicient to cause appreciable inhibition of the formation of the insoluble, non-swelling product. Such optimum proportion of inhibitor varies with the temperature of polymerization, the particular co-polymerizing agent, and the proportion in which it is used, the particular inhibitor employed, etc. but in general will be found to be between about 0.01 and about 1.0 per cent by weight of the styrene. The unsaturated ester co-polymerizing agent is usually employed in a proportion between about 1.0 and about 25.0 per cent by weightunsaturated mono-carboxylic acid and poly carboxylic acid esters of ized by heating at a 1 gives the approximate entire polymerized mass,

- parts of allyl cinnamate,

allyl, '2-methallyl, and 2-chloroallyl alcohols e. g. diallyl maleate, di-(2-chloroallyl) -oxalate, methallyl cinnamate, allyl'crotonate, 2-chl0roallyl furoate, dimethallyl succinate, etc.

' The principle of the present invention may also be applied to the improved process for preparing the insoluble and non-swelling type of styrene I co-polymer disclosed in the co-pending application of J. W. Zemba and G. H. Coleman, Serial No. 217,226, filed July 2, 1938, wherein the copolymerization is carried out in the presence of an insoluble and non-swelling co-polymer "seed in order to obtain an increased yield of the denon swelling type of co-polymer, the remaining 5 per cent bein a partially polymerized viscous liquid. A mixture of 50 parts of styrene and 4 parts of allyl cinnamate, when polymerized in the absence of an inhibitor at 80 C. for 720 hours, yielded a hard resinous product which contained only per cent of theinsoluble, nonswelling type of co-polymer.

Exemru: 3

Mixtures of purified monomeric styrene and several different unsaturated ester co-p0lymerizing agents were polymerized in the presence of a number of difierent inhibitors for the polymerization of styrene. The experimental data sired product, p 15 I together with the yields of insoluble non-swelling The following examples illustrate several Ways co-polymer obtained are tabulated below:

' Table II t Coepolymerizin'g agent Inhibitor Polymerization madam.

N g uuuan Name Percent Name Percent Time Temp.

6 Hour;68 C. 0 Percmlm 3 6 'i iiifii iliiii 'iH1551355511122"'"tit 168 80 m 3 6 2-phenylazo-6-p eny -phenol 0.2 168 so 95 4 g 2.6-di-phenylazo-4-phenyl-phenol. 0. 1 legs; 33 1% g 9 2:i-di-phenylazo-phenol 0. l 168 so 100 7 9 zfi-di-phen lezo i-phenol 0. 1 1 s 100 8 9 Phenyl-alp a-naphthyl-amine 0.1 168 so 95 9 7.5 168 so so 10 7. 5 l-amino-azobenzene 0. l 168 so 1m 11 7.5 2-phenyl-4-(2-xenylazo)-anlline 0. 1 16s 30 95 12 Do 7. 5 4-methoxy-3-phenylam-diphenyl- 0. 1 168 so o 13 Ethylene (ii- 9 168 80 5 14 o 9 2.4diphenylawphenol 0. 1 I 33 1 m t 9 12 0..ZE3?.Z3- .f?f?.i; 3 do 0.1 g e:

lhl all l-adi ate.- i; D finffilzun? 9 d0 o 1 108 so so in which the principle of the invention has been applied, but are not to be construed as limiting the same.

EXAMPLE 1 The following table presents data. illustrating J the preparation of the insoluble and non-swelling type of styrene co-polymer in the presence of several difierent inhibitors for the polymerization of styrene. In each experiment, a mixture of 50 parts by weight of commercial monomeric styrene, 2.5 parts of diallyl maleate, and the indicated proportion of the inhibitor was polymertemperature of about 80 C. for 336 hours. The last column in the table amount of the oluble, non-swelling type of co-polymer present in the the remainder being EXAMPLE 2 "A mixture of 50 parts of monomeric styrene, 2

and 0.1 part or 2.4-diphenylazo-phenol was polymerized by heating at a temperature of about 80 C. for 720 hours. The

polymerizate obtained consisted of approximately 95 per cent of the opaque, white, insoluble and Other modes of applying the principle of our invention may be employed instead of the one explained, change being made as regards the method herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated steps be employed.

We therefore point out and distinctly claim as our invention:

1. The method of preparing a white, opaque, friable, and granular styrene co-polymer which is substantially insoluble and non-swelling in benzene, which comprises polymerizing a mixture of styrene and a minor proportion of diallyl maleate at a temperature below about 110 C. in the presence of from about 0.01 to about 1.0

. per cent by weight of 2.4-diphenylazo phenol.

2. The method of preparing a white, opaque, friable, and granular styrene co-polymer which is substantially insoluble and non-swelling in benzene, which comprises polymerizing a mixture of styrene and a minor proportion of allyl cinnamate at a temperature below about C. in the presence of from about 0.01 to about 1.0 per cent by weight ofv 2.4 -diphenylazo-phenol.

3. The'method of preparing a white, opaque,

friable, and granular styrene co-polymer which is substantially insoluble. and non-swelling in benzene, which comprises polymerizing a mixtureof styrene and a minor proportion of di- (2-chloroallyl) succinate at a temperature below about 110 C. in the presence of from about 0.01 to about 1.0 per cent by weight of 2.4-diphenylazo-phenol.

4. In a method wherein a white,:opaque, friable, and granular polymerization product, which is substantially insoluble and non-swelling in benzene, is prepared by polymerizing a mixturev comprising styrene and a minor proportion of an unsaturated organic ester which contains at least two oleflnic linkages at a temperature below 110 0.; the step which consists in carrying out the polymerization in the presence of an inhibitor for the polymerization of styrene in amount willcient to inhibit the formation of the normal glass-like polymer, said amount being less than about 1.0 per cent and said inhibitor being an organic'nitrogen compound selected from the class consisting of phenyl-alpha-naphthylamine, 2-(4-phenylazo-phenoxy) ethanol, arylii azo-aryiamines and arylazo-phenols.

GERALD H. COLEMAN. JOHN W. ZEMIBA. 

